It's an interesting analysis, but I'm extremely dubious about the degree of extrapolation going on here. It's hard to imagine that the past 25 years have been t

It's an interesting analysis, but I'm extremely dubious about the degree of extrapolation going on here. It's hard to imagine that the past 25 years have been typical in human history, or for that matter that the past 125 years have been. Is it really safe to make any quantitative assumptions about how technology and society will support spaceflight 200 years from now? Those concerns are only magnified by the author's willingness to list a "nominal readiness date" of the year 5000 for humanity to be able to capture and use 100% of the entire galaxy's energy output (last line of Table 5). It would take 20 times that long just for us to reach the other edge of the galaxy, even assuming light speed travel.